The aim of the project of one-dwelling building is to conduct a study of thermal flux and
diffusion of water vapour through a part of the building cladding. By means of a computer
program, examples of structural complexes of flat roofs of two types are made – inverted flat
roof and combined flat roof. By complying to the criteria of allowed thermal transmittance of
flat roofs as are written in the PURES 2010 (Pravilnik o učinkoviti rabi energije v stavbah),
including the corresponding technical directive and the treatment of calculation method of the
thermal transmittance of building components set by the ISO 6946 standard, the effect of
different ratios of thermal insulation between the two types of flat roof on the change of
thermal flux and the corresponding needed change of the thermal insulation thickness of the
material in the system of the roofs in consideration is studied. An appendix on inverted flat
roofs is taken into account in the first part of the study of the thermal flux through structural
complexes, a correction stated in the ISO 6946 standard. The latter contains a correction on
the system’s thermal transmittance in regard to the additional heat loss due to the water
percolation through the juncture of thermal insulation layer. Additionally, an appeal for the
correction of the thermal conductivity in regard to the change of thermal conductivity of the
thermal insulation is made in the aforementioned appendix, to integrate the possible increase
of the moisture content due to the diffusion of water vapour. This subject is represented in
the second part of the study.
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